1. Technical Field
The invention relates to a system, such as a navigation system, for communicating traffic data to an operator of a vehicle.
2. Related Art
Some vehicles are equipped with a navigation system. A task of a navigation system includes determining the position of the vehicle, calculating an optimal route to a destination specified by the vehicle operator, and providing route guidance to (“routing”) the vehicle operator. For example, if the navigation system is installed in a car, the navigation system may indicate onto which direction or street to turn.
Navigation systems may include a system for processing data, and a device for determining the position of the moving vehicle that uses information from a positioning system. Digital map data relating to the road system of an area, such as that of a country, is stored on a storage medium, and may be used by the navigation system for determining a route to a final destination. Based on data relating to the position of the vehicle (the “position date”), and the route determined by the system, instructions relating to routing are communicated to the operator. The navigation system may perform routing based on actual traffic conditions. Traffic data, such as that relating to one-way streets, and turn-off restrictions may be stored with the digital map data. Such data may be regularly updated by the data supplier to provide up-to-date traffic data for navigation purposes.
Navigation systems may receive current traffic information from external information stations via a radio. The radio may have a Radio Data System function (an “RDS function”) in communication with a Traffic Message Channel (“TMC”) channel to receive traffic information. The traffic information may be received from, for example, a Short Message Service (“SMS”), or a General Packet Radio System (“GPRS”). The GPRS may use a Global System for Mobile Communication (“GSM”) unit, or a comparable wireless connection.
The traffic data provided to the navigation systems is limited by the data provided by the supplier. Therefore, information that may be of interest to a particular operator may not be available and there may not be enough memory to store such information if it were available. Furthermore, when the traffic data is received by a RDS/TMC function (which may have been encoded according to the international Standard “Alert-C-Protocol”), the data transmission capacity may be restricted to about 320 to about 430 traffic announcements per minute.